<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>弹出框案例</title>

    <script>
        var str = '啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦。\n' +
            '啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦\n啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦啦'

        alert(str);
    </script>

</head>

<body>

</body>

</html>